why the steel pipe is not bright through bright annealing process

- Sep 14, 2017 -

Whether the annealing of stainless steel tube is bright according to the following influencing factors.

(1) Whether the annealing temperature reaches the specified temperature. Temperature of stainless steel heat treatment rang in 1040~1120℃(Japanese standards). (2) Annealing atmosphere : Pure hydrogen or inert gas, but it can't contain too much oxygen and water vapor. (3) Furnace seal: The bright annealing furnace should be enclosed and isolated from the outside air. The method of inspection is apply soap water to the gaps of the joints of the annealing furnace and see if the gas is running.

(4) Protective gas pressure. In order to prevent microleakage, the protection of gas in the furnace should maintain a certain positive pressure. If it is hydrogen gas, it is usually required above 20kBar.

(5) Furnace water and steam: on the one hand, Check whether the furnace material is dry, the first charge, the furnace material must be dried. On the other hand, The stainless steel tube in the furnace can't retain moisture.